diskio: Correctly account the release of the final chunk

In incremental file processing we need to correctly account for
the final chunk being released, otherwise we end up holding a chunk
for the duration of the rest of the component for every incremental
file in the tarball.  This is what caused the issue surfaced in the
previous commit, and thus this commit fixes #2774

Signed-off-by: Daniel Silverstone <[email protected]>

src/diskio/mod.rs

@@ -422,9 +422,11 @@ pub(crate) fn write_file_incremental<P: AsRef<Path>, F: Fn(usize)>(
             let len = contents.len();
             // Length 0 vector is used for clean EOF signalling.
             if len == 0 {
+                trace_scoped!("EOF_chunk", "name": path_display, "len": len);
+                drop(contents);
+                chunk_complete_callback(len);
                 break;
-            }
-            {
+            } else {
                 trace_scoped!("write_segment", "name": path_display, "len": len);
                 f.write_all(&contents)?;
                 drop(contents);